Add a string func for allocation (#20610)

Signed-off-by: Nyangxuan <xuan.yang@zilliz.com>
Signed-off-by: Nyangxuan <xuan.yang@zilliz.com>

internal/datacoord/segment_manager.go

@@ -91,6 +91,11 @@ type Allocation struct {
 	ExpireTime Timestamp
 }
 
+func (alloc Allocation) String() string {
+	t, _ := tsoutil.ParseTS(alloc.ExpireTime)
+	return fmt.Sprintf("SegmentID: %d, NumOfRows: %d, ExpireTime: %v", alloc.SegmentID, alloc.NumOfRows, t)
+}
+
 // make sure SegmentManager implements Manager
 var _ Manager = (*SegmentManager)(nil)